Cascade reactions palladium chloride

This type of cyclization reaction was applied in the synthesis of p-carbo-linones and total synthesis of dipyrrolobenzoquinone ( )-terreusinone as well. In 2005, Barluenga and co-workers reported a novel approach for the synthesis of indoles from o-bromoanilines and alkenyl halides via a palladium-catalyzed cascade process (Scheme 2.112). The reaction involves an alkenyl amination followed by an intramolecular Heck reaction. As the authors demonstrated, this process represents the first example of the participation of alkenyl amination reactions in Pd-catalyzed cascade reactions. Initially, the relative reactivity of aiyl and alkenyl bromides and chlorides towards Pd-catalyzed amination was investigated. Competition... 

Willis has similarly noted that indoles can be prepared via the cascade coupling of the aryl-halide and vinyl-triflate bonds in styrene 21 with primary amines (Scheme 6.41). Despite the fact that two different types of C—X bonds must be activated, this process proceeds with a single palladium catalyst (Pd2dba3/Xantphos), and a range of primary amines, carbamates and amides. More recently, even vinyl chlorides were found to participate in this coupling reaction [53]. 

The one-pot synthesis of 2-substituted-3-carboxychromones is readily attained by the reaction of 3-oxo-3-(2,6-di luorophenyl)propanoates and acyl chlorides (13CC5313) and of 3-[2-(methoxymethoxy)phenyl]propio-lates and aldehydes followed by DDQ oxidation of the formed chroma-nones (13T647), via transition metal-free approaches. Palladium(II) -catalyzed cascade carbonylative cyclization of 2-bromophenols and terminal alkenes gives chromones 44 in moderate to good yields. Variation on the amine used in the catalytic system led to aurones 45 as major products (Scheme 74) (13TL1802). 

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